1. Field of Invention
The present invention relates generally to the field of multimedia content delivery, and specifically in one aspect to using available bandwidth on a content delivery network such as a cable television network in order to both optimize network operator revenue and delivery of video services to network subscribers.
2. Description of Related Technology
Modern content delivery networks such as cable television or satellite networks typically include a variety of different content and data delivery modes and associated infrastructure. For example, the typical cable television network may include a Video on Demand (VOD) portion, a broadcast delivery portion (e.g., broadcast switched architecture, such as that described on co-owned and co-pending U.S. patent application Ser. No. 09/956,688 filed Sep. 20, 2001 and entitled “Technique For Effectively Providing Program Material In A Cable Television System”, incorporated herein by reference in its entirety), DOCSIS cable modem capability, voice-over-IP (VoIP) packetized telephony, and so forth.
One significant competitive challenge presently faced by operators of content-based delivery networks relates to managing and conserving downstream bandwidth. This management and conservation includes the reclamation of otherwise under-utilized or unused bandwidth such that the service and/or customer base can be expanded without significant modifications or build-outs of the underlying network infrastructure. For example, it is desirable to expand the types and availability of “next-generation” network services, including high-definition (HD) broadcast, VOD, high-speed data, VoIP, Interactive TV, etc. over time, without the need for major capital expenditures or system modifications. Hence, network operators are increasingly focused on techniques for “squeezing” as much capacity out of their existing networks as possible.
VOD and Session Resource Managers—
Providing “on-demand” (OD) services, such as e.g., video on-demand or VOD, is well known within content-based networks. In a typical configuration, the VOD service makes available to its users a selection of multiple video programs that they can choose from and watch over a network connection with minimum setup delay. At a high level, a VOD system consists of one or more VOD servers that pass and/or store the relevant content; one or more network connections that are used for program selection and program delivery; and customer premises equipment (CPE) to receive, decode and present the video on a display unit. The content is typically distributed to the CPE over a Hybrid Fiber Coaxial (HFC) network.
Depending on the type of content made available and rate structure for viewing, a particular VOD service could be called “subscription video-on-demand (SVOD)” that gives customers on-demand access to the content for a flat monthly fee, “free video-on-demand (FVOD)” that gives customers free on-demand access to some content, “movies on-demand” where VOD content consists of movies only, and so forth. Additionally, VOD content may comprise high-definition video (e.g., HDVOD), which may be charged for example on a per-usage basis. Many of these services, although referred to by names different than VOD, still share many of the same basic attributes including storage, network and decoder technologies.
On-demand infrastructure within networks has also been adapted to the delivery of data such as computer files and the like; see, e.g., co-owned and co-pending U.S. patent application Ser. No. 11/013,665 filed Dec. 15, 2004 entitled “METHOD AND APPARATUS FOR HIGH BANDWIDTH DATA TRANSMISSION IN CONTENT-BASED NETWORKS”, incorporated herein by reference in its entirety, for one exemplary high-speed data download approach using on-demand infrastructure within a content-based network.
Just as different varieties of on-demand service offerings have evolved over time, several different network architectures have also evolved for deploying these services. These architectures range from fully centralized (e.g., VOD servers at a central location) to fully distributed (e.g., multiple copies of content distributed on VOD servers very close to the “edge” or customer premises), as well as various other network architectures there between. Since most cable television networks today consist of optical fiber towards the “core” of the network which are connected to coaxial cable networks towards the “edge”, VOD transmission network architectures also consist of a mixture of optical fiber and coaxial cable portions.
The CPE for VOD often consists of a digital cable set-top box (DSTB) that provides the functions of receiving cable signals by tuning to the appropriate RF channel, processing the received signal and outputting VOD signals for viewing on a display unit. Such a digital set-top box also typically hosts a VOD application that enables user interaction for navigation and selection of VOD menu.
While the architectural details of how video is transported in the core HFC network can be different for each VOD deployment, each generally will have a transition point where the video signals are modulated, upconverted to the appropriate RF channel and sent over the coaxial segment(s) of the network. Depending on the topology of the individual cable plant, this could be performed at a node, hub or a headend. The coaxial cable portion of the network is variously referred to as the “access network” or “edge network” or “last mile network.”
In U.S. cable systems for example, downstream RF channels used for transmission of television programs are 6 MHz wide, and occupy a 6 MHz spectral slot between 54 MHz and 860 MHz. Deployments of VOD services have to share this spectrum with already established analog and digital cable television services. For this reason, the exact RF channel used for VOD service may differ from plant to plant. However, within a given cable plant, all homes that are electrically connected to the same cable feed running through a neighborhood will receive the same downstream signal. For the purpose of managing VOD services, these homes are grouped into logical groups typically called Service Groups. Homes belonging to the same Service Group receive their VOD service on the same set of RF channels.
VOD service is typically offered over a given number (e.g., 4) of RF channels from the available spectrum in cable. Thus, a VOD Service Group typically consists of homes receiving VOD signals over the same 4 RF channels. Reasons for this grouping include (i) that it lends itself to a desirable “symmetry of two” design of products (e.g. Scientific Atlanta's MQAM), and (ii) a simple mapping from incoming Asynchronous Serial Interface (ASI) payload rate of 213 Mbps to four QAM payload rates.
In most cable networks, VOD programs are transmitted using MPEG (e.g., MPEG-2) audio/video compression. Since cable signals are transmitted using Quadrature Amplitude Modulation (QAM) scheme, available payload bitrate for typical modulation rates (QAM-256) used on HFC systems is roughly 38 Mbps. In many VOD deployments, a typical rate of 3.75 Mbps is used to send one video program at resolution and quality equivalent to NTSC broadcast signals. In digital television terminology, this is called Standard Definition (SD) television resolution. Therefore, use of MPEG-2 and QAM modulation enables carriage of 10 SD sessions on one RF channel (10×3.75=37.5 Mbps<38 Mbps). Since a typical Service Group consists of 4 RF channels, 40 simultaneous SD VOD sessions can be accommodated within a Service Group. These numbers work out very well for many deployment scenarios, such as the following example. A typical “service area” neighborhood served by a coaxial cable drop from the cable network consists of 2000 homes, of which about two-thirds are cable subscribers, of which about one-third are digital cable subscribers, of which about 10% peak simultaneous use is expected. Hence, the bandwidth required to meet VOD requirements is 2000×(⅔)×(⅓)×0.1=approximately 40 peak VOD sessions−the exact number supported by a 4 QAM service group.
The transport of data is handled by a function called the Session Resource Manager (SRM). When a new VOD session request is made, the SRM receives that request, allocates bandwidth on a downstream QAM, and sends the information back to the CPE that made the request so that it can tune to the right RF channel and the VOD program therein. Since the SRM controls mapping of incoming VOD session requests to QAM channels within the Service Group, it is an appropriate place for a network operator to enforce RF channel usage policy. In general, SRM should maximize availability of bandwidth to VOD sessions (by efficiently recycling bandwidth from expired sessions) and by ensuring some level of redundancy in case of equipment failure (e.g. a QAM modulator goes down).
More and more US households are beginning to purchase High Definition (HD) televisions (HDTV). By one estimate, by the end of 2004, over 12 million US households will have HDTV displays. To keep up with the trend, MSOs have begun offering HD television programs to cable customers and have recently started looking into deploying HD VOD services.
Entertainment-quality transmission of HD signals requires about four times as much bandwidth as SD. For an exemplary MPEG-2 Main Profile—High Level (MP@HL) video compression, each HD program requires around 15 Mbps bitrate. Although revenues from HD VOD service may not be four times the revenue from SD VOD service, the ability to offer HD VOD service is often critical to cable operators' strategy to be a leader in digital television service offerings.
Use of MPEG HD compression technology for initial deployment of HD VOD services is a logical choice, as HD VOD shares the same MPEG-2 transport layer technology. This approach allows reuse of most of the infrastructure deployed for SD VOD services. By using MPEG multiplexing techniques, SD and HD video streams can be simultaneously carried over the fiber side of the VOD network and multiplexed onto the same QAM channel in a service group. Since roughly 37.5 Mbps bandwidth is available on one QAM-256 carrier, cable operators can mix and match HD and SD VOD sessions using 3.75 Mbps per SD and 15 Mbps per HD VOD stream. For example, on a single QAM carrier, maximum 2 HD VOD sessions can be offered adding up to an aggregate 30 Mbps, with the other 7.5 Mbps being used by 2 SD sessions.
It should be recognized that under prevailing network and CPE design practices, the bandwidth required by a video stream cannot be spread over two QAM carriers. For example, when a new HD VOD session request is granted, all 15 Mbps of bandwidth must be made available on a single QAM carrier.
The role of the aforementioned SRM becomes even more important when managing a Service Group for simultaneous HD and SD VOD sessions. It has the additional task to map VOD sessions to QAM carriers such that it can ensure sufficient bandwidth block for HD VOD session on a QAM carrier in that Service Group. The method used for this mapping should at the same time be able to maximize the amount of bandwidth used without leaving bandwidth stranded on a QAM carrier. Since HD VOD takes much more bandwidth that SD video, during the introduction phase, a cable operator may wish to limit maximum number of sessions of either kind (SD or HD) allowed within a Service Group. Clearly, this number should be easily changeable (upward or downward) if business economics or other considerations demand it.
Business Considerations Relating to Network Operation—
The choice of multiple services a network operator can provide to the subscribers (e.g., broadcast, VOD, PVR/DVR, DOCSIS, VoIP, etc.) gives rise to new opportunities in terms of how to use incremental available bandwidth so as to best maximize the operator's revenue or profit. One such source of revenue or profit is third party advertising. Accordingly, the type and distribution of such advertising is a very significant determinant of network operator revenue/profits.
In conventional cable networks, advertisement revenues depend largely on the footprint of the network and the number of subscribers. Advertisements or similar promotional content may be inserted at the national level, or locally (e.g., by the network operator). The revenues generated are determined in large part based on the program stream into which the advertisements are inserted, and the time of delivery (e.g., prime-time). Advertisers may know for example that a target demographic, such as 18-30 year-old females, has a very high viewership for a certain program at a certain time. Hence, their advertisement will likely obtain a high number of “looks” or impressions, and accordingly their likely benefits in terms of such 18-30 year-old females buying their products will be higher. Accordingly, the price that can be charged for such advertising placement is accordingly high. This system may be indexed for example to third party indicia such as the well-known Nielsen Ratings.
Another important source of revenue for operators is “on demand” programming. As previously noted, subscription on-demand (e.g., SVOD) effectively allows a subscriber unlimited access to on-demand programming for a monthly or annual flat fee. HDVOD in contrast may be used as a basis for additional incremental revenue; i.e., by charging a premium or one-time fee for access to HD programming on-demand.
Free on-demand video (FVOD) provides no direct incremental revenue, but may significantly enhance subscriber satisfaction (“value add”), and may also provide indirect revenue benefits (e.g., where a subscriber sees something in the FVOD content which causes them to either request additional content or services, purchase goods over the network, etc.)
Similarly, access to high-speed data capacity (e.g., DOCSIS cable modem, or via OD infrastructure as previously described) may be an additional incremental source of revenue; premier or higher paying subscribers can be allocated additional downstream and/or upstream bandwidth for their data services. This can be on a flat fee basis (e.g., additional bandwidth for an additional $X per month), on an actual use basis (e.g., $X per Mbps actually used), offered as an incentive to premium subscribers as part of a subscription package, or any number of other approaches.
A variety of different approaches to network optimization in light of revenue or profit considerations are known in the prior art. For example, U.S. Pat. No. 7,143,431 to Eager, et al, issued Nov. 28, 2006 entitled “Method for reduced bandwidth for on-demand data streaming using mini-clusters” discloses an improvement on dynamic skyscraper delivery of continuous media programs, such as video, divides the channels used for the delivery of the video into leading and trailing groups. A cluster defining on transmission of a program can then be broken into mini-clusters in the leading group which may be freely matched to full clusters in the lower group with loosened alignment requirements. This decoupling provides more efficient allocation of bandwidth to on-demand consumer requests and permits strategic opportunities to merge requests with concurrently allocated bandwidth for similar programs.
U.S. Pat. No. 7,075,945 to Arsenault, et al, issued Jul. 11, 2006 entitled “Dynamic mapping of broadcast resources” discloses a method wherein in a data communication system such as a high capacity DBS system, dynamic mapping of broadcast resources is provided to exploit occasional redundancy in the program content of two or more input data streams, freeing at least one broadcast resource to carry alternate bitstreams, such as additional programs or existing programs at higher quality. Transmission maps defining the correspondence between input data streams and broadcast resources, and reception maps defining the correspondence between broadcast resources and output data streams, are updated as needed to dynamically modify broadcast resource mapping to increase effective utilization of available bandwidth. Beneficial n:n-y:m mapping in a high capacity consumer DBS entertainment system is provided. Apparatus and methods for generating, maintaining and updating allocation maps with reduced overhead requirements, are disclosed.
U.S. Patent Application Publication No. 20020087976 to Kaplan, et al. published Jul. 4, 2002 entitled “System and method for distributing video with targeted advertising using switched communication networks” discloses a system and method for delivering broadcast-quality video with targeted advertising to viewers over the switched communication network. According to one embodiment, program streams with appropriately inserted splice points are transmitted from a network headend node to one or more egress nodes via a switched network. Because the switched network only carries program streams while advertising is inserted at the edges of the network, programs with demographically-targeted advertising can be delivered to many different subscribers without the need for using the bandwidth of the switched network to carry a unique program and advertising stream for each demographic group from the head end node.
One significant issue or disability with the foregoing methods relates to their lack of ability to combine or consider the total cost of network operation, along with the total revenue generated. The aforementioned prior art techniques perform optimization on one aspect of available network resources (i.e. bandwidth), or perhaps increase the marginal profit (e.g. targeted advertising), without taking into account the totality of considerations needed to optimize revenues for the network operator. This is particularly true of highly complex and diversified networks which may employ multiple distinct delivery channels and paradigms; e.g., VOD, broadcast switched delivery, DOCSIS data services, etc. Each of these different portions are traditionally operated in a substantially independent manner, and without consideration of revenue or profit implications for each portion individually or the network as a whole.
Moreover, many such prior art approaches are purely aimed at operational considerations such as peak bandwidth utilization efficiency, which may or may not be compatible with revenue or profit optimization. This is particularly true in a resource-constrained environment; certain subscriber requests may have significantly greater revenue or profit impact than others, and existing session or bandwidth allocation approaches do not take this fact into consideration when arbitrating between competing requests for limited resources.
Another significant issue with prior art approaches to network optimization (including the aforementioned VOD architectures) relates to the requirement for manual intervention or input on the part of the network operator (e.g., MSO) in order to make best use of the available bandwidth. Specifically, many such systems require periodic operator adjustment or input, which may also include the requirement for periodic evaluation of the subscriber's viewing or tuning habits, and the generation of adjustments to be inserted into the system control functions based thereon. One disability with this approach is the need for constant (or near-constant) operator vigilance. Another disability is latency; the operator is basically always lagging the problem since changes in subscriber habits can occur rapidly, and the efficacy of any corrections made by the operator will in large part depend on the timeliness with which the operator performs his/her analysis and corrective action/adjustment. Greater operator vigilance is also required when the system is approaching the limits of its capacity, since excursions in demand or changes in viewer habits can easily cause an over-demand condition (potentially resulting in a loss of service to one or more subscribers for a period of time).
Hence, based on the foregoing, there is a distinct need for improved apparatus and methods that permit resource allocation based on the optimization of costs and benefits to the network operator when fulfilling a program viewing or session requests made by subscribers, especially in resource-constrained (contentious) environment. Ideally, this process could be conducted on a request-by-request (i.e., per CPE) basis if desired, and effectively in real time. Such apparatus and methods would also ideally allow for the dynamic re-evaluation and reclamation of resources (e.g., VOD sessions).
Such improved apparatus and methods would also preferably work with a set of rules defined by a network operator, without undue manual intervention, or continuous vigilance by the network operator.